Generally speaking, such a circuit includes a pump for circulating the cooling liquid, a radiator or heat exchanger in which the liquid circulates, an expansion chamber, and ducts connecting these various components to each other and to the engine. The duct for returning cooling liquid to the engine may include a thermostatically-controlled valve for closing said duct when the temperature of the liquid is low (i.e. until the engine reaches its normal operating temperature). In such an arrangement, the cooling liquid leaving the engine is generally returned directly to the engine, short-circuiting the heat exchanger. Said valve is arranged to re-establish the normal cooling liquid circuit once the temperature of the cooling liquid reaches a predetermined value.
However, even while the temperature of the engine is rising, it is advantageous, particularly in the case of diesal engines, to leave a small flow of cooling liquid thru the radiator to ensure that the liquid is degassed and to avoid the formation of hot points in the engine block. Degassing takes place in the normal manner by means of a duct connecting the upper portion of one of the radiator's water boxes to the expansion chamber. The water box used is the one which does not have the liquid inlet to the radiator associated therewith. The lower portion of the expansion chamber is connected to the suction inlet of the cooling liquid circulation pump in order to ensure the desired small flow of liquid.
Implementing this method gives satisfactory results so long as the expansion chamber is a unit independent from the radiator's water boxes. However, when the expansion chamber is part of one of said water boxes, and when it is connected to the other portion of the water box by an upper degassing duct and by a lower suction orifice, it has been observed that degassing efficiency can be greatly reduced while the operating temperature of the engine is rising, i.e. while the thermostatically-controlled valve closes the outlet tube from the radiator.
Preferred embodiments of the present invention avoid this drawback in such an integrated water box and expansion chamber device.